The Molden Format

The Molden Format is currently being used by a number of Ab Initio programs
to interface to the Molden program. Molden can convert the equivalent
information from the packages Gaussian, Gamess-US/UK and MOPAC to molden format.

Not all of the below sections are required,
you could have {[ATOMS],[GTO] and [MO]} or {[GEOCONV] with [GEOMETRIES]},
or {[FREQ],[FR-COORD],[FR-NORM-COORD], here [INT] is optional}

First Line:

[Molden Format]

Coordinates for the Electron Density/Molecular orbitals:

[Atoms] (Angs|AU)
element_name number atomic_number x y z
...

The workings are with Angstroms or Atomic Units, indicated by the
Angs or AU keyword.

Specification of the basis-set consisting of contracted Gaussian Type
Orbitals.

For 'sp' shells two contraction coefficients must be given, for both s and
p functions. g-functions are only available since molden4.4
The 0 on the shell_number line and the 1.00 on the shell_label line are
no longer functional and can be left out.

All workings with the [GTO] keyword are in Atomic Units.

Specification of the basis-set consisting of contracted Slater Type
Orbitals.

[STO]
atom kx ky kz kr alfa norm
...
atom: the number of the atom on which this orbital is centered
kx,ky,kz: the exponent of the x,y,z of the orbital
kr: the exponent of r (root of x*x+y*y+z*z) of the orbital
alfa: the alfa exponent
norm: normalization factor

All workings with the [STO] keyword are in Angstroms.

Specification of the molecular orbitals.

The molecular orbitals and their occupation number are specified in the
[MO] section. From this information a density matrix can be constructed.

Use the keyword [5D] on a separate line to specify the use of
'spherical' D and F functions (5 D and 7 F functions). The default is to
use 'cartesian' D and F functions (6 D and 10 F functions) .
The enable the use of mixed spherical and cartesian function, the
following keywords where added ([5D10F] ,[7F] (6D en 7F),[5D7F], (same as[5D], for reasons of backwards compatibility).
Since molden4.4 G-functions are also supported, default is cartesian G
functions. Use [9G] to specify spherical G functions.